This one time, at ban.... *ahem* school, I was part of an electronics class and we were doing an extra curricular session during our lunch break in the lab. Me and my mates were supposed to be making PCB's (Printed Circuit Boards) to use with our next project.
Of course, my best mate had other plans. He found some brazing rods used for welding and decided to use the buffing wheel to shine them up a bit. He took the first go, turning on the wheel and proceeding to buff the rod. It got caught in the side of the wheel and flung out of his hand, through the ceiling. Me being the fool I am, thought "Hey! That was AWESOME" and tried it myself. Needless to say, this was when it happened. The rod got caught, same as what happened to my mate, but this time, I couldn't move my hand out the way in time. Before I knew it, the rod had slashed my hand to pieces before it then flung off and almost took off my head with it. It missed my head thankfully, but my hand.... I was lucky to not lose the entire thing.
Ended up with 6 weeks off school and my hand in a sling for almost the whole duration of that time. Not to mention the stitches.... 28 in total.
tldr; don't fuck with buffing your rod on a machine which you shouldn't be using in the first place.